The present invention relates to the technical field of a gas barrier layer to be formed by plasma-enhanced CVD, more particularly to a method by which a gas barrier layer having high gas barrier quality can be formed using a substrate a surface of which is made of organic materials such as high-molecular weight compounds.
A gas barrier film (a water-vapor barrier film) having a gas barrier layer as a component is utilized not only at those sites or parts of optical devices, display apparatuses (e.g. liquid-crystal displays and organic EL displays) as well as various other devices including semiconductor devices and thin-film solar batteries which are required to be moisture-proof, but also in packaging materials used to pack foods, clothing items, electronic components, etc.
The gas barrier layer is a layer that is made of materials such as silicon oxide and silicon nitride that exhibit gas barrier quality and it is formed by a vapor-phase deposition process (vacuum deposition process) such as sputtering or CVD on a surface of the site that is required to be moisture-proof. Also used advantageously is a gas barrier film which is such that the above-mentioned gas barrier layer made of silicon nitride or the like is formed on a surface of films made of high-molecular weight materials (plastic films) or metal films.
An exemplary method of forming a gas barrier layer is plasma-enhanced CVD.
JP 11-70611 A discloses a gas barrier film comprising a substrate that is made of a transparent organic material and which has formed on one or both of its surfaces a gas barrier layer which is a silicon oxide layer having 5-15% carbon, characterized in that the gas barrier layer is formed by plasma-enhanced CVD using an organosilicon compound gas and an oxygen gas as reaction gases.
As mentioned above, the gas barrier layer is a layer that is made of materials such as silicon nitride and silicon oxide that exhibit gas barrier quality and it is formed on a surface of a substrate such as a plastic film by a vapor-phase deposition process such as sputtering or CVD.
Needless to say, the gas barrier layer is formed in a sufficient thickness to meet the gas barrier performance required by a specific use of the final product (gas barrier film).
However, if the idea disclosed in JP 11-70611 A is applied to form a gas barrier layer by plasma-enhanced CVD on a substrate such as a plastic film that has a surface made of an organic material, it often occurs that the gas barrier layer, although it has the intended thickness, fails to have the intended gas barrier performance for its specific thickness.